The objective of this research is to evaluate and provide quantitative information on structural and functional changes in capillaries for some pathophysiological states such as heart failure and shock. Specific concerns of research will be to study 1) the mechanisms of change in capillary fluid and solute exchange processes in normal and abnormal myocardial tissue in the working heart and 2) to study the mechanisms of change in capillary function which occur to promote the development of peripheral (muscle) edema and ascites in congestive heart failure. The long range goal and purpose is to provide information which will explain the specific factors responsible for interruption of those homeostatic mechanisms which control fluid balance in pathophysiological states. To fulfill this objective quantitative information pertaining to alterations in capillary hydrostatic pressure, net colloid osmotic pressure, tissue pressure, capillary surface area and capillary permeabilitY for several tissues must be obtained and correlated for pathophysiological state and compared with control. Dogs will be used as the experimental animal and procedures such as excision of tricuspid values or pulmonary artery constriction to produce right heart failure, aortic constriction for left heart failure, and excessive hemorrhaging to produce shock will be employed. The permeability surface area product of heart, skeletal muscle and intestine will be determined in the intact animal using fractional extraction of bolus injections of diffusible substances. Measurements will also be made of capillary filtration coefficients, capillary area per unit path length for solute and fluid movement, capillary equivalent pore radius, protein osmotic pressure (osmometer), capillary hydrostatic pressure, pre-and postcapillary resistance and tissue pressure (implanted capsule) using the isogravimetric and osmotic transient techniques. Control (normal) values will be compared with the specific pathophysiologic state of all parameters including statistical evaluation.